Electric heating device



Feb. 12 1924. 1,483,427

E. G. GAYNOR ET AL ELECTRIC HEATING DEVICE Fi d 1921 2 Shee'ts-Sheet 1 INVENTORS Edna .6: Gaynor lean T Wilson QTATTKQNEY Feb. 12, 1924; 1,483,427 a E. G. GAYNOR ET AL ELECTRIC HEATING DEVICE File 5. 1921 2 Sheets-Sheet 2 I 70 44 70 74 INVENTORS flGGaynm" Leon]? W 5072 J Mill/WM .fl iz ATT NEY Patented Feb. 12, 1924.

UNITED STATES PATENT OFFICE.

EDWIN G. GAYNOB, OF STRATFORD, AND LEON T. WILSON, OF-NEW HAVEN, CON- NECTICUT; SAID WILSON ASSIGNOR T0 SAID GAYNOR.

ELECTRIC HEATING DEVICE.

Application filed November 3, 1921.

To all whomv it may concern:

Be it known that we. EDWIN G. GAYNoR and Leon T. VILSON, citizens of the United States, and residents. respectively. of Stratford, county of Fairtield, State of Connecticut, and New Haven. county of New Haven, State of Connecticut, have jointly invented certain new and useful Improvements in Electric Heating Devices, of which the following is a specification.

The present invention relates to electric heating devices and in its more specific embodiment to electric fiat-irons.

In the electrically heated irons and similar apparatus heretofore used the base of the iron has commonly been heated indirectly by means of a wire positioned a short distance above the base and maintained at a high or glowing temperature by the passage of an electric current. The heat is generated in this type of heating apparatus almost entirely by the energy required to overcome the ohmic resistance of the wire and the rate at which it is generated is substantially constant for a given impressed electromotive force. The temperature of the iron is governed by the relation or balance between the rate at which heat is generated and the rate at which heat is ab stracted from the iron. When the iron is being used its temperature is maintained within a proper limit through the rapid abstraction of heat by. the moist articles being ironed but if the current be permitted to pass through the heating wire while the iron is not in use and while the abstraction of heat is therefore negligible the iron rapidly heats up until it may become red hot. \Vhen this occurs the iron is not only injured but creates a dangerous fire hazard. As the heating is silent and no warning is therefore given that the iron is in operation, there is an increased danger of leaving the current turned on while the iron is not in use with consequent danger of fire as above pointed out. Moreover, irons heated in this manner require an expensive heat resisting wire to Withstand a high temperature. The wire is necessarily much hotter than any other part of the structure because heat has to flow from the wire and heat by itself can flow only from a body of higher temerature to one of a lower temperature.

he heating efiiciency of irons of this type Serial No. 512,411.

Another object of the invention is to provide an electric heating apparatus for flat irons and similar devices-in which the temperature of the apparatus is limited to a safer value under all conditions of use during passage of the electric current.

A further object of the invention is to provide an electric heating apparatus for flat-irons and similar devices which gives an audible warning or notice when the heating current is on.

A still further objectof the invention is to provide an electric heating apparatus for fiat-irons and similar devices in which the heat is generated within the heating portion of the iron by induction from a coil or winding which is placed outside of and out of heating contact with the heating portion of the iron and which is subject to only very slight heating effects.

'With these and other objects in view the invention comprises the apparatus described and set forth in the following specification and claims.

The various features of the invention are illustrated in the accompanying drawings in which:

Fig. 1 is a top plan view with parts broken away of the flat-iron heating appa ratus embodying our invention.

Fig. 1 is a cross section on line 1--1 of Fig. 1.

Fig. 2 is an elevation of the device, the cover and a portion of the coil being shown in section on line 2-2 of Fig. 1.

Fig. 3 is an end view of the iron, the shell or cover and lead wires being removed to more clearly illustrate the inner structure.

Fig. 4 is a view of a handle bracket.

Fig. 5 is a view of a mica insulation inserted between the handle bracket and an induction coil.

Fig. 6 is a fragmentary view of a detail of modified construction.

Fig. 7 is a plan on a smaller scale of the laminated core illustrating a modified construction embodying our invention.

Fig. 8 is a side elevation, also on a smaller scale partly in section of a modified structure embodying our invention.

In the present invention the heat is generated directly in 'the base of the iron through the medium of a changing magnetic flux produced by means of an alternating current sent through an induction winding. To this end the base of the iron is connected in a closed magnetic circuit with a core about which is placed the coil or winding through which the alternating current may be sent. The core is so constructed as to have comparatively little heat generated in it. To this end and to reduce the amount of wire necessary in the coil, the core is laminated and preferably made of silicon steel or other suitable magnetic material, the coil itself having a small ohmic resistance has comparatively little heat generated in it. Moreover, it is so arranged and heat insulated as to receive but little heat from the heated portions of the iron. The coil may therefore be made of suitably insulated copper wire. Moreover, the core is mounted and positioned longitudinally of the iron so as to increase the heating at the ends and more particularly the front point which result is highly desirable and even essential in devices of this character for satisfactory service. This construction permits also the coil to be heat insulated and ventilated, thus preventing the coil from being subjected to destructive temperature.

Heat is generated in iron carrying a pulsating magnetic flux by virtue of two phe nomena known respectively as hysteresis and eddy currents. For a given flux corresponding to a given impressed electromotive force the rate at which heat is generated through hysteresis is virtually constant and independent of the. temperature except for extreme temperatures which we need not here consider. On the other hand, the rate at which heat generated by eddy currents for a given flux, changes with the temperature is due to the change in the ohmic resistance of the iron with temperature. As the ohmic resistance of iron increases with increasing temperature the amount of eddy currents and therefore the heat generated by them decreases with increasing temperature. This phenomenon has been applied to the presentinvention to reduce the rate at which heat is generated as the iron grows hotter thereby lowering the ultimate temperature which the iron will reach when left connected to the current supply without being used. To this end the base of the flat-iron is constructed of a thick (about inch) piece of commercially pure iron to permit more heating by eddy currents and less by hysteresis.

To further increase the heating by eddy currents the base of th iron is plated over with a nonferrous metal such as copper or nickel for example. The practical application of these phenomena gives an iron in which the power consumption falls as the temperature increases, and vice versa, which results are extremely desirable for the practical use ol a device of this kind.

Referring more particularly to the accompanying drawings the flat-iron is provided with a base or heating plate 10 of the usual triangular shape which is adapted to come directly into contact with the article being ironed and from which the heat is abstracted. The heat is generated directly in the heating plate or base 10 through the heating effect of rapidly changing and reversing magnetic fluxes generated in a core 12 by the action of an alternating current or currents passing through an induction winding 14 surrounding the core. The magnetic fluxes circulate from the core 12 to the base 10 through supports 16 and 18 which complete and close the magnetic circuit and serve to hold the core 12 and winding 14 spaced from and out of heat receiving position with respect to the heating plate.

The core 12 is constructed of laininations or plates which prevent the formation of eddy currents and is preferably constructed from plates of silicon steel or other iron having a very low hysteresis loss. Very little heat is therefore generated in the core or in this part of the magnetic circuit. The base of the fiat-iron is made out of a single block of very pure iron, preferably having less than 0.15 of one per cent of carbon and having a high magnetic quality and arranged to permit a maximum of eddy currents in order that a maximum amount of the energy of the changes in the magnetic flux be transformed into heat in this part of the magnetic circuit. A very high temperature coefficient of electrical resistance is also obtained through the use of iron of a high degree of purity so that the eddy currents will become less as the temperature rises, becoming very small as the temperature approaches a definite maximum limit. To increase the eddy current efi'ect the base, of the iron is provided with a coating or plating of a nonferrous. non-magnetic metal, preferably copper.

A considerable quantity of heat is also generated in the supports 16 and 18 and this heat is imparted to the base 10 at or adjacent the point and the heel of the plate which are the places at which the heat is most rapidly abstracted during use and where the greatest concentration of heat is therefore desired. The structure of the flat-iron is also such that some of the metal ill) of the base is placed beyond and around the support 16 and 18 to provide a very good path for the production of eddy currents and consequently cause the ends of the iron base to be more quickly heated. 1n the remaining portion of the iron base the heat is enerated uniformly and directly through- 'may be inserted. the bracketsbein out the heating surface thereby giving a most desirable heat distribution.

Very little heating efiect takes place in the winding 14 since the resulting currents may be comparatively small and this winding may therefore be made of ordinary copper wire suitably insulated by means of asbestos or other insulating material. In an ordinary heating iron for example a winding containing 379 turns of No. 18 B. & S. copper wire suitably insulated will befound sufticientto give the desired heating effect.

A handle 22 may be attached directl to the core 12 by means of handle brac ets 24 and 26 each having central openings as clearly illustrated through which the core positioned between the ends of the win ing 12 and the supports 16 and 18 respectively. The lower portion of each of the brackets 24 and 26 is split or broken away as'at 19 and 21 to prevent the flow of induced current in these elements. Thin plates of mica insulation 30 and 31 are placed respectively between the handle brackets 24 and 26 and the winding 14 and the supports 16 and '18. The fiat-iron is also provided with a shell) 32 provided with a suitable number of air vents 33, which covers the windings, core and supports 16 and 18 and on which is mounted a plug 34 connected to the ends 36 and 38 of the winding 14. This shell and the exposed portions of the flat-iron may be nickel plated in the usual manner. The core 12 may be attached to the supports 16 and 18 in any desired manner. In the form of the invention illustrated in Figs. 1, 2 and 6. the supports are provided with opposed grooves or slots 40 and 42 which normally are of slightly less height than the vertical thickness of the core 12. In constructing the device the core with its winding and the handle brackets 24 and 26 and mica insulating plates 30 are assembled. the supports 16 and 18 are heated until the slots or grooves 40 and 42 are expanded to permit the insertion of the core and thereafter permitted to cool and grip the core. The cover 32 may thereupon be placed in position and the plugs 34 and 35 connected respectively to the wires 36 and 38 and the handle 22 placed in position. It is found desirable to place a heat resisting sheet or slab 44, preferably of as bestos, on and over the plate 10 extending underneath the core 12 and winding 14 and surrounding the supports 16 and 18.

As shown in Fig. 6 the wires 36 and 38 may lead through a protectin conduit 37 on the handle bracket 24 or ot erwise suitably placed, the wires 36 and '38 thus forming a cord or line 39 as usual in similar installations; the circuit being,-of course, controlled by a switch (not shown) in any approved manner.

\Vhen the device is connected in an electric circuit and the current is on the rapid alternations ofcurrent in the winding 14 .induce rapidly changing ma netic fluxes in the core 12 which circulate hack and ,forth through the core, end supports 16 and 18 and the base 10. Owing to the slight opportunity provided for hysteresis and eddy currents in the core 12 andthe low c-urrent in the winding 14 very little heat is generated in this part of the iron. A comparatively large heating effect is however obtained in the plate 10 and the posts or supports 16 and 18 owing to the comparatively greater eddy currents set up in this part of the apparatus by the magnetic fluxes generated in the core 12. As these parts of the device increase in temperature the heating effect decreases since the increase in electrical resistance of the iron with the temperature opposes the eddy currents. The iron therefore tends to remain within a lower temperature limit, which in this type of iron is 350 degrees C. for all conditions of use and to positively avoid the production of excessively high temperatures when the current is accidentally left on while the iron is not being used. When the current is on the rapid changes in current and fluxes cause a humming sound which serves as an audible signal to warn the operator of this condition. Through this humming signal and the limitation of the temperature obtainable the fire risk is very much reduced and through the direct manner of heating the iron the efiiciency is increased and the power consumption is decreased.

In Figs. 7 and 8 we have indicated a modified and somewhat simplified form of structure by means of which the core 12' with its winding 14 may be secured to the heating plate 10- through supports 16' and 18 and by means of screws S as shown. I

The core is made up of laminated metal strips in the manner above described and shaped into a point 50 at its forward end so that the ends of the laminations will have the same shape as the block 18 which is also triangular in shape. The rear block 16 is rectangular in shape and the rear end of the laminated core is also of the same horizontal dimension and shape.

The handle brackets are secured to the core before it is mounted by springing the lower ends therearound, each plate fitting in the grooves 51 and 52, as shown in Figs. 7 and 8. This structure is then mounted in the manner hereinabove set forth with respect to the forms shown in Figs. 1, 2 and 6.

The core is preferably provided with a layer 43 of suitable heat insulation such as asbestos, and the supports 16 and 18 may also be covered with a similar layer of heat insulation as at 46 and l8. This insulation may be also effected in any other approved manner as by lining the covering shell 32 with such material.

- Having thus described my invention what we claim as new and desire to secure by Letters Patent is:

1. An electric heating device comprising a magnetic circuit comprising a heating plate formed of iron containing less than 0.15 per cent of carbon, and an induction winding on a portion of said magnetic circuit outside of said plate.

2. An electric heating device comprising a heating plate, an iron core connected in closed magnetic circuit with said heating plate, said plate being formed of iron containing less than 0.15 per cent of carbon, and an induction coil surrounding said core.

8. An electric heating device comprising a heating plate, an iron core in magnetic circuit with said plate and an induction winding on said core, said core having a lower hysteresis loss than said plate.

4. An electric heating device comprising a heating plate. a silicon iron core having a low hysteresis loss in magnetic circuit with said plate and an induction winding on said core, the composition of said core and plate and proportions of said magnetic circuit being such as to limit the maximum temperature of said plate.

5. An electric heating device comprising a heating plate, supports on said plate, said supports having opposed slots, a core closely fitted between the walls of said slots and an induction winding on said core.

6. An electric heating device comprising a heating plate of very pure iron, a nonferrous, non-magnetic plating on said plate, supports on said plate, a laminated core of silicon iron mounted on said supports and an induction winding on said core.

7. An electric heating device comprising a heating plate, supports on said plate, a core mounted on said supports, an induction winding on said core and a handle having brackets mounted on said core between said winding and said supports.

8. An electric heating device comprising a heating plate, supports on said plate, a core mounted between said supports, an induction winding on said core, a handle having brackets mounted on said core between said winding and said supports and a mica insulation between said brackets and said winding 9. An electric heating device for fiatirons and similar apparatus which comprises a heating plate having a. non-ferrous, non-magnetic p ating, supports on said plate, a core having a minimum hysteresis effect mounted between said supports and an induction winding on said core.

10. An electrical heated flat-iron which comprises a heating plate having supports, a core mounted between said supports. an induction winding mounted on said core between said supports, a handle having brackets mounted on said core between said winding and said supports, a vented covering shell enclosing said supports, core and induction winding and permitting said handle brackets to project therethrough.

11. An electric heating device for flatirons and similar apparatus which comprises a heating plate, supports on said plate at each end thereof, a portion of said plate extending outwardly beyond said supports, a core positively secured at each end to said supports and an induction winding on said core.

12. An electric heating device comprising a heating plate having a high eddy current effect when magnetized, an iron core having a relatively low hysteresis loss, in magnetic circuit. with said plate, and an induction winding on said core.

13. An electric heating device comprising a heating plate having a high eddy current effect when magnetized, a core of silicon iron having a low hysteresis 10$ in magnetic ircuit with said plate, and an induction windin on said core.

igned this first day of November, 1921.

EWDIN G. GAYNOR. LEON T. WILSON. 

